1. Field of the Invention
The present invention relates to a hydraulic actuator, and more precisely, relates to a multi-stage hydraulic actuator having an outer cylinder and an inner cylinder.
2. Description of Related Art
In a conventional hydraulic cylinder device, a single piston is usually reciprocally moved in a cylinder. A multi-stage cylinder device is also known, in which an auxiliary cylinder is provided in addition to a main cylinder. To carry out sequential operations using such a multi-stage cylinder device, it is usually necessary to actuate a plurality of cylinder devices in accordance with a predetermined sequence. This, however, results in complex and expensive operations.
The primary object of the present invention is to therefore provide a single hydraulic actuator in which a plurality of operations can be sequentially effected by a simple cylinder device.
Another object of the present invention is to provide a simple hydraulic actuator which ensures a precise operation without an eccentric load which would be otherwise applied thereto.